feat: Add log processing script to opa for decision logging

[xeniape]

Description

Part of stackabletech/opa-operator#422

This PR adds the script which is used in the opa start command set by the opa-operator to filter incoming logs by log level and route logs to the correct output (file or console).

Definition of Done Checklist

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1. Changes are OpenShift compatible
2. All added packages (via microdnf or otherwise) have a comment on why they are added
3. Add an entry to the CHANGELOG.md file
4. Integration tests ran successfully https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/opa-operator-it-custom/96/

TIP: Running integration tests with a new product image

The image can be built and uploaded to the kind cluster with the following commands:

bake --product <product> --image-version <stackable-image-version>
kind load docker-image <image-tagged-with-the-major-version> --name=<name-of-your-test-cluster>

See the output of bake to retrieve the image tag for <image-tagged-with-the-major-version>.

[NickLarsenNZ]

Nice script. If you haven't already, it might pay to run it through the shellcheck linter.

[sbernauer]

Very nice, exactly what I was thinking of! Haven't properly reviewed the operator part yet, feel free to wait with merge until both are ready to be merged.
Also happy about @siegfriedweber's review

[siegfriedweber]

LGTM